Receipts from hundreds of patrons of a local restaurant

have a symmetric distribution ranging from a minimum

of $20 to a maximum of $170, with a median of $90.

Which of these is the best estimate of the standard

deviation?

Kindy see the explanation section 

Step-by-step explanation

For a symmetric distribution

Median = Mean 

Thus 

Mean = 90

Min = 20

Max = 170 

Usually 99.87% of the data do fall within 3 standard deviations from the mean

Thus 

Approximate standard deviation = (max - mean)/ 3  =  (170 - 90)/3 = 26.67

Or 

std dev = (Max - Min) / 6 = (170-20)/6 = 25

So chose any of the two is an estimate..

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NOTE

The above is a general procedure:

So you can comment with the options then we get the correct one form the options given.